Speaking to "Erin Burnett OutFront" from his home in Saginaw, Texas, Rick Zamarripa fought back tears remembering his son, Patrick.

"Since he was born he was a hero, he was my little hero, and he is a big hero. He's a big hero now," said the grieving father. "He's going to be missed."

Patrick Zamarripa was a U.S. Navy veteran who served in Iraq and Kuwait. His father, clutching a framed photo of his son in uniform, spoke of the close bond they shared, and said they would even text each other while Patrick was on the job.

Thursday evening, as the elder Zamarripa watched developments unfold on TV, he wasn't able to reach his son. After a pair of phone calls with his daughter-in-law, Rick Zamarripa went to the hospital.

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"I was greeted by one of his partners that he graduated (with) at the police academy, and I said, 'How's Patrick doing?'" Zamarripa recalled. "He just looked at me and his face started turning red, and I knew right there and then, and I said, 'No.'"